In the current integrated circuit (IC) or electronic devices, the heat dissipating device has a bottom plate and a heat dissipating unit. The bottom plate has a plurality of trenches. Fins are inserted into the trenches. The method for fixing the fins to the bottom plate can be referred to FIG. 1. The bottom plate 10 of the heat dissipating device 1 is formed with trenches 11. The bottom plate 10 is fixed to the fixture (not shown). Then they are fixed below a punching device 12. The punching device 12 has a plurality of weights 13. The weights 13 are driven by a puncher to move upwards and downwards. The weights 13 pass through the gaps between the fins 14 to collide a surface of the bottom plate 10 so that the fins 14 are riveted into the bottom plate 10. Thus a heat dissipating device 1 is formed.
With the progress of the chip and IC technologies, more and more heats are generated and are concentrated in some predetermined parts of the devices and the increment of temperature is more and more rapid. To have high heat dissipating ability, the material of the heat dissipating device 1 is improved, such as using copper to replace aluminum. Further, more fins 14 are planted in the bottom plate 10 so as to increase the heat dissipating area. As a result, the density of the fins 14 on the bottom plate 10 is increased. To cause the weights 13 can be inserted into the gaps between the fins 14 and thus they can punch the bottom plate 10. However this will break the bottom plate 10. Moreover, the fins 14 have errors so that the weights 13 cannot be accurately aligned to the gaps between fins 14. As a result, in the punching process, it is possible that the fins 14 will be destroyed and thus the yield ratio is low. Thereby the weights 13 are possibly destroyed in the punching process. However the weights 13 are expensive.